The Dahuang Wubeizi powder is a multi-component botanical active pharmaceutical ingredient supplied as a veterinary-grade powder. It contains gallotannins, gallic acid, and anthraquinone glycosides in lot-dependent proportions, which makes dose standardization dependent on assayed extractable solids rather than a fixed weight/weight formula across dosage forms. The following downstream applications are limited to existing veterinary dosage routes where a botanical astringent/antibacterial powder of this type is actually processed: non-sterile tablets, hard capsules, oral soluble powders, medicated premixes, sterile injectables, and non-sterile oral granules. The powder is not a single excipient and is not interchangeable with purified tannic acid.

At the tablet press, the as-received powder is not directly compressible. Its angle of repose normally exceeds 40°, tap density ranges between 0.45 g/cm³ and 0.65 g/cm³, and the high gallotannin fraction binds to moisture-sensitive fillers during storage. Tablet manufacture therefore requires a wet granulation step prior to lubrication. The API is pre-blended at 20–35% w/w of the final core, using microcrystalline cellulose PH 101 or PH 102 and lactose monohydrate as diluents; the exact addition ratio is adjusted against the lot assay for total tannins, because loading above 35% w/w without increasing the binder level leads to granule yield below 60% and tablet hardness below 5 kp on a rotary press. Incompatibility is observed with protein binders such as gelatin; the gallotannins can cross-link with the protein at 55–60 °C drying temperatures, producing a granule cake that cannot be milled by an 18-mesh screen. A 5% w/w pregelatinized starch paste or 3% w/w hydroxypropyl methylcellulose solution is used as the binder; the binder is added in a high-shear mixer at impeller speed 250–350 rpm for 6–10 min. The wet mass is passed through an 18-mesh screen, dried at 55–60 °C to a loss on drying of ≤3.0% w/w per USP <731>, then milled to a granule fraction between 40 and 80 mesh. Magnesium stearate at 0.5% w/w is added as a lubricant; however, the hydrophobic lubricant must be blended for no more than 3 min at 15–20 rpm in a V-blender, because over-lubrication increases disintegration time beyond the 15 min limit of USP <701>. Compression on a rotary tablet press with 8.0 mm round flat-faced punches uses a compression force of 8–12 kN, producing tablets with hardness 5–8 kp, friability ≤0.8% w/w per USP <1216>, and disintegration ≤15 min in water at 37 ± 2 °C. Dissolution testing per USP <711> uses 900 mL of simulated gastric fluid without pepsin and a paddle speed of 50 rpm; the release of gallic acid equivalents is used as the marker. Each batch is released under 21 CFR 211.165 with assay, dissolution, hardness, and microbial limits per USP <61> and USP <62>. The finished product is a 300–500 mg oral tablet for swine or calves, with batch-to-batch hardness variation controlled within ±0.8 kp by storing granules in sealed containers with a desiccant when ambient relative humidity exceeds 60%.

Premix and Medicated Feed Carryover Limits Under 21 CFR 225

A medicated premix does not begin at the final feed mixer. The first unit operation is a screen-based de-lumping step through a 20-mesh sieve because the raw powder contains fibrous rhubarb residue and gallnut shell fragments that can segregate in a ribbon mixer. The standardized botanical API is incorporated at 10–20% w/w into a 5 kg intermediate carrier consisting of ground corn cob or rice hulls with a particle size distribution of 600–850 μm. This preconcentrate is blended until the coefficient of variation for a gallic acid marker is ≤5.0%, measured by three-dimensional mixer sampling at 10 points. The intermediate is then diluted into a commercial premix at 1:10 or 1:20, resulting in a final complete-feed inclusion of 1–2% w/w for the veterinary oral route. Batch-to-batch variance in tannin content of ±8% requires adjustment of the premix dilution factor after each lot assay; this is not a fixed recipe. The mixing equipment must be validated for carryover because tannin-rich fines adhere to ribbon blades and mixer walls, creating cross-contamination risk. Clean-in-place procedures per 21 CFR 225.30 and 21 CFR 225.42 require complete removal of residues before a different API is used. Metal detection and a final screening through 12-mesh are performed before packaging. The finished product form is a 5% w/w or 10% w/w medicated premix powder for feed mills, intended for further dilution into complete feed. Compliance with 21 CFR 225 and 21 CFR 558.3 applies in the United States, while EU feed mills follow Regulation (EU) 2019/4 for medicated feed production and homogeneity. Published data for the exact carryover threshold of this botanical powder under commercial feed mill conditions is limited; therefore, a conservative carryover residue limit of ≤1% of the lowest active premix concentration is applied during cleaning validation.

When the target dosage form is drinking-water administration, the powder's high tannin fraction imposes solubility and nozzle-related constraints that do not appear in dry dosage forms. The raw API cannot be simply blended with dextrose and packed, because gallotannins precipitate in hard water and create turbidity, leading to clogged nipple drinkers and dose variability. The production route therefore starts with a hot-water extraction of the powder at 90–95 °C for 2 h; the extract is filtered through 10 μm bag filters and centrifuged at 3000 × g for 15 min to remove insoluble rhubarb pectin and gallnut shell fines. The clarified liquid is concentrated to 20–25% w/w solids under vacuum at 60–70 °C to avoid thermal degradation of gallotannins. Spray drying follows using a rotary atomizer at inlet temperature 170–180 °C and outlet temperature 75–85 °C; maltodextrin with dextrose equivalent 10–15 is added as a carrier at 30–50% w/w of total solids, and colloidal silicon dioxide is added at 0.5–1.0% w/w as an anti-caking agent. The resulting spherical powder must have a particle size distribution of 80–120 mesh and a moisture content of ≤5.0% w/w per USP <731> to remain free-flowing. In the final product, the API concentration is adjusted to deliver 0.5–1.0 g/L of the original standardized extract when dissolved in drinking water; the exact addition ratio in the packaged powder is derived from the extraction yield, which normally loses 25–35% of the raw powder mass. The finished product is a 100 g or 500 g oral soluble powder in moisture-barrier sachets or jars, intended for automatic drinking water proportioners in swine and poultry barns. Compliance for water quality follows USP <1231> for pharmaceutical water used in manufacture; cleaning of spray dryer and baghouse filters follows 21 CFR 211.67; residual solvent testing is performed per VICH GL18 for any ethanol used during extraction. Failure to centrifuge before spray drying results in nozzle clogging within 20–30 min and is the most common batch-rejection cause on commercial lines.

Capsule Fill Mass, Bulk Density, and Granule Tensile Strength

Hard capsule production rejects the raw powder because its angle of repose commonly exceeds 42° and its bulk density can be below 0.35 g/mL, causing unstable fill mass when using automatic capsule filling machines. The corrective step is dry granulation by roller compaction, not wet granulation, because water can initiate gallotannin polymerization with residual starch and reduce capsule dissolution. The API is blended with microcrystalline cellulose and pregelatinized starch to a final API load of 30–50% w/w in the fill blend. Roller compaction is performed at roll pressure 25–35 kN and roll speed 3–5 rpm on a compactor with 1.0 mm knurled rolls; the ribbons are milled through a 16-mesh screen to produce granules with a tensile strength of 0.8–1.2 MPa. The granule fraction between 40 and 80 mesh is selected for encapsulation; fines below 80 mesh are recycled once because repeated fines generation reduces bulk density and flow. A 0.25% w/w sodium stearyl fumarate is used as the lubricant instead of magnesium stearate, as the latter can slow the release of tannins in acidic capsule dissolution media. Capsule filling on an automatic capsule machine with a size 1 or size 0 gelatin or hypromellose capsule uses a target fill mass of 250–500 mg and a fill-weight variation tolerance of ±5.0% per USP <905>. Disintegration time is checked per USP <2040> and must not exceed 15 min in water; dissolution per USP <711> uses 900 mL of 0.1 N hydrochloric acid at 37 ± 0.5 °C, with a paddle speed of 50 rpm. The finished product is a 250 mg or 500 mg hard capsule for oral administration to companion animals or calves, packed in high-density polyethylene bottles with desiccant. Ambient relative humidity above 60% during encapsulation can raise granule moisture to above 3.0% w/w, causing capsule shell brittleness and fill-weight drift; therefore, the encapsulation suite is maintained at 35–45% RH and 20–25 °C.

What Is Recoverable When Sterile Injection Is Required After Gallotannin Removal?

Unlike the dry capsule route, sterile injection of this botanical powder is not a direct milling or dilution operation; the as-received material carries insoluble cell-wall fragments, bacterial endotoxins, and a high molecular weight gallotannin fraction that is incompatible with terminal steam sterilization. The API must first be converted into a purified injectable-grade extract. Aqueous extraction is performed with purified water at 80–90 °C for 2 h; the extract is then subjected to ethanol precipitation by adding ethanol to a final concentration of 60–70% v/v and holding at 2–8 °C for 24 h to precipitate polysaccharides and proteins. The supernatant is clarified by centrifugation at 4000 × g for 20 min, then passed through a 10 kDa molecular weight cut-off polyethersulfone ultrafiltration membrane at transmembrane pressure 0.2–0.4 MPa. This ultrafiltration removes the insoluble high-tannin aggregates and reduces the bioburden load, but it does not guarantee depyrogenation. The permeate is adjusted to pH 6.5–7.5 with 0.1 N sodium hydroxide; the solution is then filtered through a 0.45 μm prefilter and a 0.22 μm sterilizing-grade polyvinylidene fluoride filter. Terminal steam sterilization at 121 °C for 15 min is avoided because residual gallotannins can hydrolyse, resulting in colour darkening and visible precipitation; aseptic filtration is therefore the method of choice. The final formulation contains 0.5–2.0 mg/mL total phenolic compounds expressed as gallic acid equivalents, diluted with sterile water for injection and sodium chloride to isotonicity. Published data for the exact clinical dose of Dahuang Wubeizi injectable in target species is limited; therefore, the loading range is a manufacturing benchmark rather than a therapeutic dose claim. The finished product is a 10 mL single-dose or 100 mL multi-dose aqueous injection vial intended for intramuscular use after additional target-species safety studies. Compliance is anchored to USP <1> for injections, USP <85> for bacterial endotoxins, USP <790> for visible particulates, and 21 CFR 211.110 for in-process sampling; aseptic processing follows EU GMP Annex 1 with Grade A filling conditions.

When the Powder Must Remain Dispersible Without a Liquid Blister Pack

Because the oral granule route avoids the high compaction forces of tablets, granulation can proceed at lower compression force, but the resulting granules must be tightly sized for uniform dosing from a scoop or top-dressing application. The raw powder must pass both a 60-mesh screen and a moisture specification of ≤3.0% w/w; otherwise the gallnut-derived tannin fraction binds to the granulator screen and reduces yield below 70%. The API is fluid-bed granulated with a 10–15% w/w maltodextrin solution and a total API load of 15–30% w/w on a dry basis. Inlet air temperature is set at 60–70 °C, product temperature at 35–40 °C, and atomization air pressure at 1.5–2.0 bar on a top-spray fluid bed with 6 L capacity. The spray rate is adjusted to maintain the outlet relative humidity below 50%, because higher moisture causes agglomeration and the formation of oversize granules above 12 mesh. The dried granules are sieved to 12–18 mesh and can be packed directly. The granule formulation contains no more than 1.0% w/w colloidal silicon dioxide to improve flow without reducing dispersibility in oral dosing syringes. The finished product is a 1 g or 5 g unit-dose oral granule stick or bulk jar for administration by top-dressing feed in calves, lambs, and goats. The process is monitored for uniformity of dosage units per USP <905> and loss on drying per USP <731>; batch release includes microbial enumeration per USP <61> and specified microorganisms per USP <62>. Compared to the premix route, this route uses no final feed dilution and therefore requires stricter control of the addition ratio in each unit dose, because a ±10% weight variation can shift the delivered tannin dose outside the intended target in neonatal animals.